This invention relates to an automatic apparatus for conjointly sewing two elastic cloths having different elasticity and in particular for the sewing of an elastic cloth onto another elastic cloth having a lower elasticity and being of substantially annular shape. The most important application for such an apparatus is in the clothing field and particularly in the field relating to the manufacturing of corsets, underwears, slip-stockings (collants), bathing suits and the like.
For a better understanding of the present invention, with the term "cloth" it is meant any woven or knitted fabric (wool, silk, flax, synthetic fibers and the like), the elasticity of which depends on the own elasticity of the yarns or on the manufacturing method (i.e. weaving, knitting and similars). With the term "piece" it is meant any manufactured product formed by at least two conjointly sewed cloths to be possibly subjected to further operations.
It is known that a sewing of this type has been so far obtained by manually joining two elastic cloths by means of a conventional sewing machine, which has to be controlled by a single operator. The operator in order to obtain a good seam, has to manually transfer the two cloths to be joined under head of a sewing machine and has further to provide for maintaining the correct relative position of said joined cloths until the completion of the sewing cycle.
Attempts have been effected to partially eliminate the drawbacks due to such a manual work by providing several devices adapted to be applied to the head of the sewing machine in order to carry out at least a part of the manual work entrusted to the operator. Such devices usually comprise mechanical stress regulators, slides, supports and pressing shoes which assist the operator to whom however the task of carrying out the sewing operation is still entrusted and whose intervention is essential for obtaining a proper joint of the cloths.
From the above it results that the pieces thus obtained are costly if compared to the employed labour cost and scarcely reliable as to their quality. As a matter of fact, the time spent by a single operator excessively affects the production cost of the finished piece, and this without taking into account the considerable time spent for training the operator to that specific task, which task requires a good specialization. Moreover, the quality of the finished piece manufactured by the same operator may change from piece to piece and, in any case, it changes anytime the operator is changed.